There are so many beginners out there who can’t grasp or just don’t believe the importance of resting for muscle growth. Training for hours every single day will not give you huge muscle, in fact in may even do the opposite.
If you are over training and not giving your muscles enough time to recover, your muscle will actual start to deteriorate. When you are training with weights, if you are putting enough stress on them by lifting heavy enough, you are actually damaging the fibres within the muscle. Once this has happened, with enough rest and nutrition, the muscle will begin to repair. Only it will repair itself stronger and thicker than it was before, so it will be able to handle the weight you were lifting to damage it in the first place. If you do not allow the muscle enough time to repair itself, you will continue to damage already damaged muscle tissue. This will eventually start to weaken this muscle, having negative effects on growth.
So remember, more is not always better when exercising for muscle growth. Allow enough time for the exercised muscle to repair and grow, don’t train the same body parts every day. Use Split routines and introduce sufficient rest days into your workout plan.